"Furthermore, as much as there are local law issues in places like NYC against them, I don't anticipate those lasting long or having a large effect on their revenues."
If this is true, it will also apply to their competitors, right? Either the prices of Marriott will fall if/when they stop charging some crazy-expensive taxes on their guests, or AirBnb will have to start paying/charging for those taxes. One way or another, it'll change. Right now, one of AirBnb's advantages is that they are ignoring zoning restrictions and the like; either those restrictions will go away or they'll have to play by those rules.
To me, the biggest thing AirBnb has going for them is that they are choosing to play fast-and-loose with the laws, and hoping that they can grow fast enough to change them (similar to Uber). That gives them a huge advantage against the established businesses who have to play by the rules. Marriott can't just say "we're going to build a giant hotel in this area that isn't zoned for it", but AirBnb can hide behind its hosts because presumably they hold all the liability.
I imagine there will be some pushback at some point where AirBnb presumably makes most of their money: in big metropolitan areas. In Boston, where I'm at, these are generally illegal/against rental policies. People tend to look the other way for now, but at some point it might become a bigger issue. For me, personally, when I was setting up my condo association, myself & the other owners specifically wrote it into our documents that AirBnb and short-term-rentals are NOT allowed without prior authorization.
On a separate note, I wonder what percentage of the hotel revenue is business travel. I know in companies I've worked for in the past, they had some pretty good deals set up with hotel chains, so no matter where you traveled, you stayed at whatever the preferred chain was.